In present time division duplex (TDD) systems, such as for example, the TD-SCDMA (Synchronous Code Multiple Access) systems, a user terminal, a UE, can be handed over between different base stations depending on the received signal strength at the UE. The base stations in such systems are usually referred to as NodeB. One function of the NodeB is to route all traffic to and from UEs within a certain area in the system, a so called “cell”.
Thus, if the signal strength from the NodeB to which the UE is at present “attached” falls below a certain level, and there is another NodeB whose signal the UE receives stronger, the UE can be handed over from the present NodeB to the new Node B. i.e. the NodeB with the higher signal strength.
In some systems, the strength of the signal which the UE receives from its NodeB is reported by the UE to the NodeB. In the TD-SCDMA system, this is done by means of a parameter known as P-CCPCH RSCP, Primary Common Control Physical Channel Received Signal Code Power. Thus, the NodeB transmits a “beacon” signal on the channel known as P-CCPCH, and the UE reports the P-CCPCH RSCP to the NodeB. Based on these reports, decisions are made regarding handover of the UE between different NodeBs. A special time slot in the system is usually dedicated to the transmission of the P-CCPCH.
A problem in this context is that the P-CCPCH RSCP only reflects the received signal strength from the NodeB in the P-CCPCH down link channel, which is transmitted in a certain time slot. Thus, for example, signal deficiencies in other channels/time slots than the one used by the NodeB for the P-CCPCH channel will not lead to a handover of the UE to another NodeB, although such deficiencies may seriously degrade the performance of the UE.